Losing power at high revs - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 21 (permalink) Old 06-16-2016, 03:51 PM Thread Starter
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Losing power at high revs

Gents,

I took the bike out today for a good shake down post build and it's all good but for one thing, at around 7.5k + it feels rough and almost missing. The power definitely dips off the curve, it's still revving and pulling but definitely not pulling as well..

Thoughts?

My first port of call is probably plugs.. what do you guys think?

PCV with a LDB map installed but not specifically to my bike.

Any ideas?

Cheers fella's

Jay

Last edited by MJay; 06-16-2016 at 04:18 PM.
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post #2 of 21 (permalink) Old 06-16-2016, 04:05 PM
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Who's map and for what region bike? A US Spec bike does not utilize the same mapping as a UK spec bike or a Japan Spec bike etc.

Iridium plugs need more frequent changing than conventional plugs, but that is only good for a couple hp mostly observed at around peak hp

As we discussed I'm thinking you are just feeling the effects of the stock gearing since the bike doesn't have enough hp to pull redline like that. You have to lower the gearing in order to be able to able to get the engine to rev out and use all the available rpms.
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post #3 of 21 (permalink) Old 06-16-2016, 04:15 PM Thread Starter
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OK fair point Mike. The map is for a EU bike so as a base should be ok.. well I would have thought so. I hear you on the gearing but it happens from 3rd onwards.. if it was 6th I would say gearing, but I certainly won't rule that out. I remember having my old bike flat out many times, it wouldnt hot the limiter in top but it was a quite a linear delivery.
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post #4 of 21 (permalink) Old 06-16-2016, 04:38 PM
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Hey what battery you running in that thing?

& tell me more about the exhaust. Is that a proper HRC Superbike exhaust fitted to an otherwise stock engine with Ladybird cans? The huge diameter exhausts from the SBK machines never worked properly on even mildly built production based engines.

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post #5 of 21 (permalink) Old 06-16-2016, 04:48 PM Thread Starter
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At the moment a stock battery (for now before I get a Speedcell)
the exhaust has reduced headers compared to the full factory HRC kit. I believe it should run fine with a stock motor unlike the full HRC kit which needs the engine build to go with it.
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post #6 of 21 (permalink) Old 06-16-2016, 04:55 PM
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Maybe she's just not as fast ya remember
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post #7 of 21 (permalink) Old 06-16-2016, 05:21 PM Thread Starter
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That is distinctly likely but it won't put me off it. I was a little worried that the mods would take the character out of it but I needn't have worried. It's got it all in spades.
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post #8 of 21 (permalink) Old 06-16-2016, 07:51 PM
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how about an issue with the relocated tip over sensor?
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post #9 of 21 (permalink) Old 06-16-2016, 08:55 PM
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Quote:
Originally Posted by MJay View Post
Gents,

I took the bike out today for a good shake down post build and it's all good but for one thing, at around 7.5k + it feels rough and almost missing. The power definitely dips off the curve, it's still revving and pulling but definitely not pulling as well..

Thoughts?

My first port of call is probably plugs.. what do you guys think?

PCV with a LDB map installed but not specifically to my bike.

Any ideas?

Cheers fella's

Jay
Possible lean Air/Fuel situation at that rev range using that exhaust/map combo.
If the A/F gets too lean, you'll notice power fade and possible misfiring if too lean.

Happened to me right after I took delivery of my bike in 2008.
Prior owner installed a Jardine 2 to 1 and a PCIIIr, but I doubt he had it mapped on a dyno.
At around 5600 RPM, the power started to fade big time, and at 5800 RPM it began misfiring. If I pushed on past 6000 RPM, it picked itself up and ran fine.

All I did was have it mapped on a dyno and it ran just fine across the full rev range afterwards.
Plugs showed a nice amber/honey color and worked fine.
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post #10 of 21 (permalink) Old 06-16-2016, 11:35 PM Thread Starter
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Originally Posted by dansp1 View Post
how about an issue with the relocated tip over sensor?
Maybe but it is at the same angle as before.. hmm
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